package com.sapuo.enroll.utils;

/**
 *  详细介绍类情况
 * @Author xu_huan
 * @Since 2012-12-26
 * @See
 */
public class Base64 {
    private static final byte[] encodingTable = { 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81,
            82, 83, 84, 85, 86, 87, 88, 89, 90, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111,
            112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 43, 47 };

    private static final byte[] decodingTable = new byte[128];

    static {
        for (int i = 65; i <= 90; ++i) {
            decodingTable[i] = (byte) (i - 65);
        }

        for (int i = 97; i <= 122; ++i) {
            decodingTable[i] = (byte) (i - 97 + 26);
        }

        for (int i = 48; i <= 57; ++i) {
            decodingTable[i] = (byte) (i - 48 + 52);
        }

        decodingTable[43] = 62;
        decodingTable[47] = 63;
    }

    public static byte[] encode(byte[] data) {
        int modulus = data.length % 3;
        byte[] bytes;
        if (modulus == 0) {
            bytes = new byte[4 * data.length / 3];
        }
        else {
            bytes = new byte[4 * (data.length / 3 + 1)];
        }

        int dataLength = data.length - modulus;

        int i = 0;
        for (int j = 0; i < dataLength; j += 4) {
            int a1 = data[i] & 0xFF;
            int a2 = data[(i + 1)] & 0xFF;
            int a3 = data[(i + 2)] & 0xFF;

            bytes[j] = encodingTable[(a1 >>> 2 & 0x3F)];
            bytes[(j + 1)] = encodingTable[((a1 << 4 | a2 >>> 4) & 0x3F)];
            bytes[(j + 2)] = encodingTable[((a2 << 2 | a3 >>> 6) & 0x3F)];
            bytes[(j + 3)] = encodingTable[(a3 & 0x3F)];

            i += 3;
        }
        int d1;
        int b1;
        int b2;
        switch (modulus) {
        case 0:
            break;
        case 1:
            d1 = data[(data.length - 1)] & 0xFF;
            b1 = d1 >>> 2 & 0x3F;
            b2 = d1 << 4 & 0x3F;

            bytes[(bytes.length - 4)] = encodingTable[b1];
            bytes[(bytes.length - 3)] = encodingTable[b2];
            bytes[(bytes.length - 2)] = 61;
            bytes[(bytes.length - 1)] = 61;
            break;
        case 2:
            d1 = data[(data.length - 2)] & 0xFF;
            int d2 = data[(data.length - 1)] & 0xFF;

            b1 = d1 >>> 2 & 0x3F;
            b2 = (d1 << 4 | d2 >>> 4) & 0x3F;
            int b3 = d2 << 2 & 0x3F;

            bytes[(bytes.length - 4)] = encodingTable[b1];
            bytes[(bytes.length - 3)] = encodingTable[b2];
            bytes[(bytes.length - 2)] = encodingTable[b3];
            bytes[(bytes.length - 1)] = 61;
        }

        return bytes;
    }

    public static byte[] decode(byte[] data) {
        byte[] bytes;
        if (data[(data.length - 2)] == 61) {
            bytes = new byte[(data.length / 4 - 1) * 3 + 1];
        }
        else if (data[(data.length - 1)] == 61) {
            bytes = new byte[(data.length / 4 - 1) * 3 + 2];
        }
        else {
            bytes = new byte[data.length / 4 * 3];
        }

        int i = 0;
        byte b1;
        byte b2;
        byte b3;
        byte b4;
        for (int j = 0; i < data.length - 4; j += 3) {
            b1 = decodingTable[data[i]];
            b2 = decodingTable[data[(i + 1)]];
            b3 = decodingTable[data[(i + 2)]];
            b4 = decodingTable[data[(i + 3)]];

            bytes[j] = (byte) (b1 << 2 | b2 >> 4);
            bytes[(j + 1)] = (byte) (b2 << 4 | b3 >> 2);
            bytes[(j + 2)] = (byte) (b3 << 6  | b4 & 0xff);

            i += 4;
        }

        if (data[(data.length - 2)] == 61) {
            b1 = decodingTable[data[(data.length - 4)]];
            b2 = decodingTable[data[(data.length - 3)]];

            bytes[(bytes.length - 1)] = (byte) (b1 << 2 | b2 >> 4);
        }
        else if (data[(data.length - 1)] == 61) {
            b1 = decodingTable[data[(data.length - 4)]];
            b2 = decodingTable[data[(data.length - 3)]];
            b3 = decodingTable[data[(data.length - 2)]];

            bytes[(bytes.length - 2)] = (byte) (b1 << 2 | b2 >> 4);
            bytes[(bytes.length - 1)] = (byte) (b2 << 4 | b3 >> 2);
        }
        else {
            b1 = decodingTable[data[(data.length - 4)]];
            b2 = decodingTable[data[(data.length - 3)]];
            b3 = decodingTable[data[(data.length - 2)]];
            b4 = decodingTable[data[(data.length - 1)]];

            bytes[(bytes.length - 3)] = (byte) (b1 << 2 | b2 >> 4);
            bytes[(bytes.length - 2)] = (byte) (b2 << 4 | b3 >> 2);
            bytes[(bytes.length - 1)] = (byte) (b3 << 6  | b4 & 0xff);
        }

        return bytes;
    }

    public static byte[] decode(String data) {
        byte[] bytes;
        if (data.charAt(data.length() - 2) == '=') {
            bytes = new byte[(data.length() / 4 - 1) * 3 + 1];
        }
        else if (data.charAt(data.length() - 1) == '=') {
            bytes = new byte[(data.length() / 4 - 1) * 3 + 2];
        }
        else {
            bytes = new byte[data.length() / 4 * 3];
        }

        int i = 0;
        byte b1;
        byte b2;
        byte b3;
        byte b4;
        for (int j = 0; i < data.length() - 4; j += 3) {
            b1 = decodingTable[data.charAt(i)];
            b2 = decodingTable[data.charAt(i + 1)];
            b3 = decodingTable[data.charAt(i + 2)];
            b4 = decodingTable[data.charAt(i + 3)];

            bytes[j] = (byte) (b1 << 2 | b2 >> 4);
            bytes[(j + 1)] = (byte) (b2 << 4 | b3 >> 2);
            bytes[(j + 2)] = (byte) (b3 << 6  | b4 & 0xff);

            i += 4;
        }

        if (data.charAt(data.length() - 2) == '=') {
            b1 = decodingTable[data.charAt(data.length() - 4)];
            b2 = decodingTable[data.charAt(data.length() - 3)];

            bytes[(bytes.length - 1)] = (byte) (b1 << 2 | b2 >> 4);
        }
        else if (data.charAt(data.length() - 1) == '=') {
            b1 = decodingTable[data.charAt(data.length() - 4)];
            b2 = decodingTable[data.charAt(data.length() - 3)];
            b3 = decodingTable[data.charAt(data.length() - 2)];

            bytes[(bytes.length - 2)] = (byte) (b1 << 2 | b2 >> 4);
            bytes[(bytes.length - 1)] = (byte) (b2 << 4 | b3 >> 2);
        }
        else {
            b1 = decodingTable[data.charAt(data.length() - 4)];
            b2 = decodingTable[data.charAt(data.length() - 3)];
            b3 = decodingTable[data.charAt(data.length() - 2)];
            b4 = decodingTable[data.charAt(data.length() - 1)];

            bytes[(bytes.length - 3)] = (byte) (b1 << 2 | b2 >> 4);
            bytes[(bytes.length - 2)] = (byte) (b2 << 4 | b3 >> 2);
            bytes[(bytes.length - 1)] = (byte) (b3 << 6  | b4 & 0xff);
        }

        return bytes;
    }
}